KABUL - Three US Marines have been shot dead by an Afghan worker on a military base in southern Afghanistan, in a deadly 24 hours for NATO-led forces during which six American soldiers were killed in rogue attacks.

The shooting took place on Friday night in the Garmsir district of Helmand province, where three US special forces soldiers were killed by an Afghan policeman and comrades earlier in the day.

"Let me clearly say that those two incidents clearly do not reflect the overall situation here in Afghanistan," the chief NATO force spokesman, Brigadier-General Gunter Katz, told reporters on Saturday.

The three Marines were shot by a base employee who turned a gun on them, in the third rogue attack in four days. Foreign military sources said the man had not been wearing a uniform and it was unclear how he got hold of the weapon.

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